THREAD JOINT

Description

Technical Field of the Invention

[0001] The present invention relates to a thread joint intended for percussive rock drilling.

Prior Art

[0002] Thread joints in drill strings are exposed to large loads in percussive top hammer drilling, wherein the drill string has the object of transferring percussive energy from a top hammer to a carbide-tipped drill bit at the free end of the drill string. Usually (see for example WO 8 203 653), the individual drill rod has, at an end, a formed female thread intended to receive a male thread at an opposite end of another drill rod. In connection with drilling, for removing drill dust out of the bore hole as well as lubricating and cooling the drill bit, water is usually used as flushing medium, possibly with certain additives, e.g. for improving the lubrication. The drill steel, i.e. the material in bits, bars, tubes, sleeves and shank adapters, is during drilling exposed to abrasive and corrosive attacks. In particular, this is the case in drilling underground where water is used as flushing medium and where the environment generally is damp. The attacks are especially serious in parts having relatively small diameters, i.e. at thread ends or thread clearances 5, the latter one of which is illustrated in Fig. 3 connected to a sleeve 4 of a drill bit. The flushing medium with drill dust travels in the return direction A at a relatively high speed. Thereby, vortex vortices B are formed at marked dimension-changes.

Objects and Features of the invention

[0003] The present invention aims at obviating the above-mentioned problems and at providing an improved thread joint for percussive rock drilling, which additionally improves the efficiency in modern mining.

[0004] Another object of the present invention is to provide a thread joint, which reduces the formation of vortex vortices in percussive drilling.

[0005] Another object of the present invention is to provide a thread joint at which blasting effects and corrosion from exterior flushing medium is reduced.

[0006] According to the invention, said objects are attained by the features given in the characterizing portion of claim 1. Preferred embodiments of the thread joint according to the invention are further defined in the dependent claims.

Brief Description of the Appended Drawings

[0007] In the drawings:

Fig. 1A

shows a view of a thread joint according to the present invention shown partly in longitudinal section,

Fig. 1B

shows an enlarged section according to the line B-B in Fig. 1A, and

Fig. 2

shows a view corresponding to Fig. 1A showing an alternative embodiment of the invention.

Fig. 3

shows formation of vortex vortices at a prior art device.

Detailed Description of Preferred Embodiments of the Invention

[0008] The present invention relates to a thread joint 10 for percussive rock drilling between a first drill rod 11 and a sleeve 13, preferably integrally fastened to a drill bit 12, as is shown in Fig. 1. Alternatively, the sleeve may be integrally fastened to a second drill rod or to a connector tube, not shown. The sleeve 13 has a cylindrical outer surface 28. The drill bit 12 comprises a front surface 29 that accommodates a plurality of front buttons 30 and peripheral buttons 31, only two of which are shown in Fig. 1A. The peripheral buttons 31 define the diameter of the drilled hole in a conventional way.

[0009] The drill rod 11, and thereby the thread joint, comprises at least one conduit 14 for transportation of flushing medium, such as water. Said conduit 14 connects to at least one conduit 15 in the drill bit 12. The drill rod 11 has a hexagonal radial cross-section and comprises a first outer surface 16. The drill rod may alternatively have a circular cross-section. The first outer surface 16 has a first outer diameter D1, i.e. the largest diametrical dimension between two corners in the hexagon in a radial cross-section, which is substantially constant in the axial direction. The drill rod 11 has a first end 17 or spigot provided with a male thread 18, such as a rope thread or trapezoidal thread, for percussive drilling. The male thread 18 comprises a concave thread entrance or thread start 19 and a concave thread exit or a thread end 20. The first end 17 comprises a first end surface 21. The first drill rod 11 comprises a second outer surface 22 having an outer second diameter D2. The second outer surface 22 is turned or ground to an accurately defined diameter D2 and has an axial extension from 1 mm to 50 mm. The second outer surface 22 is axially arranged between the first outer surface 16 and the thread end 20. The sleeve 13 comprises a recess 23 that comprises a female thread 24 and an inner stop face 25. The recess 23 connects to a second end surface 26 of the sleeve. The second end surface 26 is substantially ring-shaped. A substantially cylindrical inner surface 27 is arranged between the second end surface 26 and the female thread 24. The inner surface 27 has an inner diameter D3. The thread joint 10 becomes mounted when the spigot 17 has been threaded into the recess 23 until the first end surface 21 abuts against the inner stop face 25. At a mounted thread joint, the dimensions of the parts are arranged in such a way that the second end surface 26 of the sleeve is arranged axially beyond the thread end 20 of the male thread 18 or a thread clearance 33' (see Fig. 2), so that at least a part of the inner surface 27 conceals the weakest cross-section of the first drill rod. The weakest cross-section of the drill rod is the part of the drill rod that has the smallest cross-sectional area, such as at the thread end 20 of the male thread 18 or at the thread clearance 33'. The second end surface 26 of the sleeve is then arranged in a plane P, which intersects the second outer surface 22 axially beyond the thread end 20 of the male thread 18. The distance X between the thread end 20 and the plane P is at least 1 mm. Thus, the second end surface of the sleeve is arranged at least 1 mm axially beyond the thread end of the male thread.

[0010] The inner diameter D3 of the inner surface 27 is at least equally large as, maximum 1 mm larger than, the outer second diameter D2 of the second outer surface 22 but smaller than the first outer diameter D1 of the first outer surface 16. The chosen dimensions give relatively small geometrical transitions between the parts 11 and 12 for decreasing the extent of vortex vortices, so that the effect on the extension joint from drill dust and aggressive water decreases. The flushing medium may alternatively consist of an admixture of air and water.

[0011] The relatively small geometrical transitions may also be described by defining a first imaginary cylinder C1, which constitutes an axial extension of the inner surface 27 and a second imaginary cylinder C2, which constitutes an axial extension of the outer surface 28 of the sleeve 13, see Fig. 1B. The first imaginary cylinder C1 intersects the drill rod 11 while the second imaginary cylinder C2 extends outside of the drill rod. Thereby, vortex vortices in the transitions or the joints are minimised at the same time as the control of the drill string in the borehole is improved. Both the imaginary cylinders C1 and C2 intersect the peripheral buttons 31.

[0012] The outer surface 28 of the sleeve 13 has a third outer diameter D4, which is larger than the first outer diameter D1 of the first outer surface 16.

[0013] It should be noted that the thread end of the male thread may be arranged within the axial area that the female thread defines and that the cylindrical surface then surrounds a thread clearance and at least a part of the turned or ground second outer surface.

[0014] Fig. 2 shows an alternative embodiment of a thread joint 10' according to the present invention. Equal parts have been designated with the same reference designations as in Figs. 1A and 1B. The thread joint 10' has a drill rod 11' and a rock drill bit 12' for percussive drilling. The drill bit 12' has a sleeve 13' having a recess 23' wherein a relatively long, turned or ground inner surface 27' and the female thread 24 are arranged. The outer surface of the sleeve is denominated 28'. The drill rod 11' has a threaded spigot or end 17' and a relatively long, turned or ground second outer surface 22'.

[0015] What foremost makes this embodiment different from the one above-described is that the second outer surface 22' and the inner surface 27' have been made axially longer, whereby abutment between the same may be attained along the distance X', so that also an improved control of the rock drill bit 12' is obtained. Furthermore, it is outlined in Fig. 2 that a sealing ring 32, i.e. an O-ring or the like, may be arranged in the inner surface 27' of the sleeve 13' for further decreasing the vortex vortices and the circulation close to the end surface 26 of the sleeve 13'. Furthermore, the embodiment according to Fig. 2 comprises a thread clearance 33'. The thread clearance 33' consists of a circumferential concave recess, which enables clearance for thread tools in chasing of threads of the male thread. The distance X' is in this case measured between the plane P and the thread clearance 33' and is at least 1 mm. Thus, the second end surface of the sleeve is arranged at least 1 mm axially beyond the thread clearance 33'.

[0016] Conventional hexagonal and round rock drill rods are rolled and the accuracy in the circumferential direction becomes relatively poor why it is chosen in the thread joint according to the present invention to turn or grind the inner surface 27, 27' for enabling a good abutment between the surfaces 22, 22' and 27, 27'.

[0017] Thus, the present invention relates to a thread joint intended only for percussive rock drilling, preferably by means of top hammer drilling. The thread joint 10 is formed in order to reduce the formation of vortex vortices in percussive drilling by minimising dimension differences between parts included in the joint. The dimensions of the joints are chosen such that blasting effects and corrosion from exterior flush water are reduced and are directed towards greater dimensions of the joint.

Claims

1. Thread joint for percussive rock drilling between a first drill rod and a sleeve fastened to a drill bit (12;12'), to a second drill rod or to a connector tube, wherein the thread joint (10;10') comprises at least one conduit (14) for transportation of flushing medium, such as water,
wherein the first drill rod (11;11') has a first outer surface (16) having a substantially axially constant, largest first outer diameter (D1) as well as a first end (17;17') provided with a male thread (18), such as a rope thread or trapezoidal thread, for percussive drilling, wherein said male thread (18) comprises a thread start (19) and a thread end (20), wherein the first end comprises a first end surface (21), wherein the first drill rod (11;11') comprises a second outer surface (22;22') having an outer second diameter (D2), wherein the second outer surface (22;22') is arranged axially between the first outer surface (16) and the thread end (20),
wherein the sleeve (13;13') comprises a recess (23;23') comprising a female thread (24) and an inner stop face (25), wherein the recess connects to a second end surface (26) of the sleeve, wherein the second end surface (26) is substantially ring-shaped, wherein a substantially cylindrical inner surface (27;27') is arranged between the second end surface and the female thread, wherein the inner surface has an inner diameter (D3),
characterized in that, in a mounted thread joint (10;10'), the second end surface (26) of the sleeve is arranged axially beyond the thread end (20) of the male thread (18) or a thread clearance (33') so that at least a part of the inner surface conceals the weakest cross-section of the first drill rod, such as the thread end of the male thread (18) or the thread clearance (33') and in that the inner diameter (D3) of the inner surface is at least equally large as the outer second diameter (D2) of the second outer surface (22;22') and smaller than the first outer diameter (D1) of the first outer surface (16) and in that a first imaginary cylinder (C1) constitutes an axial extension of the inner surface (27;27') and a second imaginary cylinder (C2), which constitutes an axial extension of an outer surface (28;28') of the sleeve (13;13') and in that the first imaginary cylinder (C1) intersects the drill rod (11;11') while the second imaginary cylinder (C2) extends outside of the drill rod.

2. The thread joint according to claim 1, characterized in that the second end surface (26) of the sleeve is arranged at least 1 mm axially beyond the thread end (20) of the male thread (18) or the thread clearance (33').

3. The thread joint according to claim 1 or 2, characterized in that the sleeve (13; 13') has a third outer diameter (D4), which is larger than the first outer diameter (D1) of the first outer surface (16).

4. The thread joint according to any one of claims 1-3, characterized in that the inner diameter (D3) of the inner surface is maximum 1 mm larger than the outer second diameter (D2) of the second outer surface (22;22').

5. The thread joint according to any one of claims 1-4, characterized in that the second outer surface (22;22') is machined to a cylindrical shape, such as by means of turning or grinding.

6. The thread joint according to claim 6, characterized in that both imaginary cylinders (C1,C2) intersect peripheral buttons (31) of the rock drill bit (12;12').

Ansprüche

1. Gewindeverbindung zum Schlagbohren für Gestein zwischen einer ersten Bohrstange und einer an einem Bohrer (12; 12'), an einer zweiten Bohrstange oder an einem Verbindungsstutzen befestigten Hülse, worin die Gewindeverbindung (10; 10') zumindest einen Kanal (14) zur Beförderung von Spülmedien, wie etwa Wasser, umfasst,
worin die erste Bohrstange (11; 11') eine erste Außenoberfläche (16) mit einem im Wesentlichen axial konstanten, größten ersten Außendurchmesser (D1) sowie ein erstes Ende (17; 17'), das mit einem Außengewinde (18), wie etwa einem Seilgewinde oder einem Trapezgewinde, zum Schlagbohren bereitgestellt ist, aufweist, worin das Außengewinde (18) einen Gewindeanfang (19) und ein Gewindeende (20) umfasst, worin das erste Ende eine erste Stirnoberfläche (21) umfasst, worin die erste Bohrstange (11; 11') eine zweite Außenoberfläche (22; 22') mit einem zweiten Außendurchmesser (D2) aufweist, worin die zweite Außenoberfläche (22; 22') axial zwischen der ersten Außenoberfläche (16) und dem Gewindeende (20) angeordnet ist,
worin die Hülse (13; 13') eine Vertiefung (23; 23') umfasst, die wiederum ein Innengewinde (24) und eine Innenanschlagfläche (25) umfasst, worin die Vertiefung mit einer zweiten Stirnoberfläche (26) der Hülse verbindet, worin die zweite Stirnoberfläche (26) im Wesentlichen ringförmig ist, worin eine im Wesentlichen zylindrische Innenoberfläche (27; 27') zwischen der zweiten Stirnoberfläche und dem Innengewinde angeordnet ist, worin die Innenoberfläche einen Innendurchmesser (D3) aufweist,
dadurch gekennzeichnet, dass die zweite Stirnoberfläche (26) der Hülse in einer befestigten Gewindeverbindung (10; 10') axial über das Gewindeende (20) des Außengewindes (18) oder eines Gewindezwischenraums (33') hinausgehend so angeordnet ist, dass zumindest ein Teil der Innenoberfläche den schwächsten Querschnitt der ersten Bohrstange, wie das Gewindeende des Außengewindes (18) oder den Gewindezwischenraum (33'), überdeckt, dass der Innendurchmesser (D3) der Innenoberfläche zumindest gleich groß wie der zweite Außendurchmesser (D2) der zweiten Außenoberfläche (22; 22') und kleiner als der erste Außendurchmesser (D1) der ersten Außenoberfläche (16) ist, dass ein erster gedachter Zylinder (C1) eine axiale Verlängerung der Innenoberfläche (27; 27') darstellt und ein zweiter gedachter Zylinder (C2) eine axiale Verlängerung einer Außenoberfläche (28; 28') der Hülse (13; 13') darstellt und dass der erste gedachte Zylinder (C1) die Bohrstange (11; 11') schneidet, während der zweite gedachte Zylinder (C2) sich außerhalb der Bohrstange erstreckt.

2. Gewindeverbindung nach Anspruch 1, dadurch gekennzeichnet, dass die zweite Stirnoberfläche (26) der Hülse zumindest 1 mm axial über das Gewindeende (20) des Außengewindes (18) oder des Gewindezwischenraums (33') hinausgehend angeordnet ist.

3. Gewindeverbindung nach einem der Ansprüche 1 oder 2, dadurch gekennzeichnet, dass die Hülse (13; 13') einen dritten Außendurchmesser (D4) aufweist, der größer als der erste Außendurchmesser (D1) der ersten Außenoberfläche (16) ist.

4. Gewindeverbindung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass der Innendurchmesser (D3) der Innenoberfläche maximal 1 mm größer als der zweite Außendurchmesser (D2) der zweiten Außenoberfläche (22; 22') ist.

5. Gewindeverbindung nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die zweite Außenoberfläche (22; 22') in Form eines Zylinders, wie etwa durch Mittel zum Drehen oder Schleifen, bearbeitet ist.

6. Gewindeverbindung nach Anspruch 6, dadurch gekennzeichnet, dass beide gedachte Zylinder (C1, C2) periphere Knöpfe (31) des Steinbohrers (12; 12') schneiden.

Revendications

1. Raccord fileté pour le forage à percussion de roche entre une première tige de forage et un manchon fixé à un foret (12 ; 12'), à une seconde tige de forage ou à un tube de connecteur, dans lequel le raccord fileté (10 ; 10') comprend au moins un conduit (14) pour le transport d'un milieu de rinçage, tel que de l'eau,
dans lequel la première tige de forage (11 ; 11') a une première surface externe (16) ayant un plus grand premier diamètre externe sensiblement axialement constant (D1) ainsi qu'une première extrémité (17 ; 17') dotée d'un filetage mâle (18), tel qu'un filetage de câble ou un filetage trapézoïdal, pour le forage à percussion, dans lequel ledit filetage mâle (18) comprend un début de filetage (19) et une fin de filetage (20), dans lequel la première extrémité comprend une première surface d'extrémité (21), dans lequel la première tige de forage (11 ; 11') comprend une seconde surface externe (22 ; 22') ayant un second diamètre externe (D2), dans lequel la seconde surface externe (22 ; 22') est située de manière axiale entre la première surface externe (16) et la fin du filetage (20),
dans lequel le manchon (13 ; 13') comprend un évidement (23 ; 23') comprenant un filetage femelle (24) et une face de butée interne (25), dans lequel l'évidement se raccorde à une seconde surface d'extrémité (26) du manchon, dans lequel la seconde surface d'extrémité (26) est sensiblement en forme de bague, dans lequel une surface interne sensiblement cylindrique (27 ; 27') est située entre la seconde surface d'extrémité et le filetage femelle, dans lequel la surface interne a un diamètre interne (D3),
caractérisé en ce que, dans un raccord fileté (10 ; 10') monté, la seconde surface d'extrémité (26) du manchon est située de manière axiale au-delà de la fin du filetage (20) du filetage mâle (18) ou d'un jeu de filetage (33') de sorte qu'au moins une partie de la surface interne dissimule la section transversale la plus faible de la première tige de forage, telle que la fin du filetage du filetage mâle (18) ou le jeu de filetage (33') et en ce que le diamètre interne (D3) de la surface interne est au moins aussi grand que le second diamètre externe (D2) de la seconde surface externe (22 ; 22') et plus petit que le premier diamètre externe (D1) de la première surface externe (16) et en ce qu'un premier cylindre imaginaire (C1) constitue une extension axiale de la surface interne (27 ; 27') et un second cylindre imaginaire (C2), qui constitue une extension axiale d'une surface externe (28 ; 28') du manchon (13 ; 13') et en ce que le premier cylindre imaginaire (C1) coupe la tige de forage (11 ; 11') alors que le second cylindre imaginaire (C2) s'étend à l'extérieur de la tige de forage.

2. Raccord fileté selon la revendication 1, caractérisé en ce que la seconde surface d'extrémité (26) du manchon est située au moins à 1 mm axialement au-delà de la fin du filetage (20) du filetage mâle (18) ou du jeu de filetage (33').

3. Raccord fileté selon la revendication 1 ou 2, caractérisé en ce que le manchon (13 ; 13') a un troisième diamètre externe (D4) qui est plus grand que le premier diamètre externe (D1) de la première surface externe (16).

4. Raccord fileté selon l'une quelconque des revendications 1 à 3, caractérisé en ce que le diamètre interne (D3) de la surface interne est au maximum 1 mm plus grand que le second diamètre externe (D2) de la seconde surface externe (22 ; 22').

5. Raccord fileté selon l'une quelconque des revendications 1 à 4, caractérisé en ce que la seconde surface externe (22 ; 22') est usinée selon une forme cylindrique, telle qu'au moyen du tournage ou du moulage.

6. Raccord fileté selon la revendication 6, caractérisé en ce que les deux cylindres imaginaires (Cl, C2) coupent des boutons périphériques (31) du foret à roches (12 ; 12').

Drawing